Valve-operating mechanism for regenerative furnaces



C. P. TURNER vALvn OPERATING MECHANISM Fon REGENE-RATIVE FUnNAcEs Filed NOV. 2. 1921 8 Sheets-Sheet 1 M Gummi,

Oct. 13, 1925. 1,556,811

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' Oct. 13, 1925- 1,556,811 c. P. TURNER VALVE OPERATING IIECHANISI FOR REGENERATIVE FURNACES Filed NOV. 2, 1921 8 Sheets-Sheet 5 oa. 13, 192s. 1,556,811

C. P. TURNER VAL" rmrxne uncmmlsl F011 nEasnEnA'rIvn rumumss Filed Nov. 2, 1921 8 Sheets-Sheet 4 KM Bumm 15.

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G Q s m l Norway Oct. 13, 1925.

c. P. TURNER- VALVE. OPERATING IECHANISI FOR REGENEMTIVE FURNACES Filed Nov. 2, 1921 8 Sheets-Smet` 6 Chimneys 13l 1925. 1,556,811 c. P. TURNER VALVE OPERATING IECHANISM FOR REGENERATIVIE PURNACES M WMM m13 mg/mm,

Patented Oct. 13, 1925.

UNITED STATES CHARLES PRENTICE TURNER, OF STEELTON, PENNSYLVANIA.

VALVE-OPERATING MECHANISM FOR- BEGENERATIVE FURNACES.

Application filed November To all whom t may con-cern Be it known that I, CHARLES PRENTICE TURNER, a citizen of the United States, and residing at Steelton, Dauphin County, State of Pennsylvania, have invented certain new and useful Improvements in Valve-Operating Mechanism for Regenerative Furnaces, of which the following is a specification.

The present invention relates to mecha nism for operating the reversing valves of regenerative furnaces.

In the usual operation of regenerative furnaces, particularly open hearth furnaces, a combustible gas, such as producer gas, and atmospheric air, are led through separate channels or conduits. to the hearth or combustion chamber, where they are allowed to intermingle and where combustion of the gas takes place. The hot gases of combustion pass from the opposite end of the furnace through two similar conduits to the stack or first to one or more waste-heat boilers and thence to the stack. Valves are provided by means of which the direction of flow of air and gas to the furnace and the Yflow of hot waste gases therefrom may be controlled or reversed, and a checker chamber is provided in each of the gas conduits, the brick checkerwork in these chambers being heated to high temperatures when the exhaust gases from the furnace are passing therethrough, and serving to heat the incoming gas and air when the direction of gas flow has been reversed.

A serious difficulty met with in furnaces of this character resides in the tendency for explosions of considerable magnitude to occur at the time of reversal. These explosions are due to the fact that at each reversal of the furnace, a considerable quantity of unburned gas, which has been highly heated in the checker chamber but has not yet reached the combustion chamber, flows toward the stack and is mixed with a quantity of highly heated air, the inter-mingling of these two gases causing their sudden ignition or detonation. In modern open hearth furnaces waste heat boilers are frequently used, through which the hot gases of combustion are passed before they flow to the stack to escape to the atmosphere, and by means of which a considerable saving of heat is effected. lVhere such boilers are employed the explosion of unburned gas upon a reversal of the furnace is particularly un- 2, 1921. Serial No. 512,304.

desirable iu that the boiler settings, brick work and connecting flues, may be seriously damaged.

lt has been found that these explosions may be avoided if the hot unburned gas is allowed to flow through the boiler to the stack before the air conduit is opened. upon cach reversal of the furnace, so that no intermixture of hot gas and air can -take place, unless it takes place in the stack, where, if there actually is an explosion, it is harmless in effect. In accordance with this method of operation, at each reversal of the furnace, the valve controlling the flow of heated air to the stack is the last to be opened, and is only opened after the unburned tgases have made their escape.

The object of this invention is to provide a mechanism for conveniently accomplishing the reversal of a regenerative furnace and by means of which the valves are open-ed and closed in the necessary sequence to prevent all explosions. Electro-mechanical valve operating `devices are provided which are controlled by a single master switch, the operation of this master switch by the furnace attendant at the desired time being all that is necessaryY to effect the reversal of the furnace.

Each valve is provided with an individual electro-mechanical valve operating device and circuit making and breaking mechanism controlled by the master switch automatically opens and closes the circuits to the several valve operating devices so that these are energized and deenergized in the desired sequence. In my tto-pending application, Serial No. 512,303 filed Nov. 2, 1921, an apparatus is described in which a single motor is provided for operating all of the valves, this motor being connected to the valves mechanically and being controlled by a single master switch, as in the present instance. In some cases it is impossible or undesirablek to employ a mechanism as outlined above and described in my co-pending application, inasmuch as the mechanical difficulties of connecting all of the valves to the single operating motor are too great. In such cases the individual valve operating devices described in the present application are particularly useful.

The present mechanism has many novel features, as will be apparent to one skilled in the art, as it is disclosed in the following description and in the accompanying drawings in which: 0

Figure 1 is a plan view of the gas intake and outlet passages of a regenerative open hearth furnace, portions being broken away to show the interior of the checker chambers and flues;

Figures 2, 3 and 4 are sections on lines 2-2, 3-3 and 4 4, respectively, of Figure 1 Figure 5 is a side elevation of a valve and the valve operating mechanism associated therewith;

Figure 6 is an end view of the same;

Figure 7 is a side view of circuit maklng and breaking mechanism controlling the c1rcuits to the individual valve operating motors;

Figures 8, 9 andlO are sections on lines 8 8, 9--9, and 10-10, respectively of Figure 7 Figure 11 is a diagrammatic representa,- tion of certain motor control circuits;

Figure 12 is a series of diagrams, showing the circuits through the various valve operating motors, and the sequence in which such circuits are established in the operation of the mechanism;

Figure 13 is a side elevation of a valve and a modified form of valve operating mechanism;

Figure 14 is an end View of the same;

Figure 15 is an enlarged view of a motion stopping mechanism adapted to be used with the valve operating device shown in Figure 13;

'Figure 16 is a side elevation of a device for opening and closing in predetermined sequence circuits through the several modified valve operating devices;

Figures 17, 18 and 19 are sections on lines 17-17, 18-18 and 19-19 respectively of Figure 16;

Figure 20 is a diagram showing the arran ement of certain electrical circuits; igure 21 is also a diagram showing the arrangement of circuits and parts for moditying the operation of the circuit opening and closing device illustrated in Figure 16, and

Figure 22 is a series of diagrams showing the positions of the valves and the sequence of establishment of circuits through the individual valve operating devices, in successive steps, Which will result from the use of the modified apparatus illustrated in Figures 13 to 20 inclusive.

The hearth, or chamber in which the gases are actually burned is not illustrated in the drawings but it will be understood that the horizontal flues 10, 11, 12 and 13 are the gas and air conducting flues, lues 10 and 13 being the gas lues and ues 11 and 12 the air flues, and that each flue is adapted to conduct its gaseous contents in either direction. constitute chambers for containing the usual checker work, which is not shown. The ow of gases through the respective flues is controlled by valves which are illustrated diagrammatieally in Figure 1 and indicated at GF, G5, AS, AF, A'F, AS, GS, and G", respectively. The main gas intake is illustrated at 14 and is connected by Hues 15 and 16 to flues 10 and 13, respectively, the direction of flow of gas being controlled by valves Gxr and GF. The stack is indi,- cated at 17 and flues 18 and 19 respectively connect each of the four flues 10, 11, 12 and 13 to this stack, the valves G, A, As, and Gs controlling the openings between the last mentioned flues and llues 18 and 19. Valves A and AF control the ow of fresh air into dues 11 and 12. y

In the tops of flues 18 and 19are valve controlled openings 20 and 21 which communicate with the Waste-heat boiler or boilers andl dampers 22 and 23 are' provided for blocking fines 18 and 19 so that the hot a products of combustion cannot escape directly to the stack but must pass first through the waste-heat boiler setting.

The normal positions of the valves when flues 10 and 11 are serving as gas and air inlet flues respectively and flues 12 and 13 as outlet flues for the hot products of combustion are indicated in Diagram 1 of Figure 12. In this figure it will be seen that valves GF', AI". A'E and Grs are in raised or open position while the remaining valves are closed. In Diagram 4 of Figure 12 the positions of the various valves have been reversed so that the Enlargements 10', 1l', 12 and 13' flow through the conduits 10, 11, 12 and 13 is reversed. Diagrams 2 and 3 indicate theA positions of the valves at two intermediate st ages during the reversal. In Diagram 2 all of the valves are shown closed and in Diagram 3 the air valve to the stack As has not yet been opened while valves Gs, A and \i GF are shown in open position. Diagrams 5 and 6 show the two intermediate stages in a second reversal of the valves, from the positions which they appear in Diagram 4 to the positions which they appear in Diagram 1. lDiagrams 3 and 6, when taken in connecltion with Diagrams 4 and 1 show clearly that tra in the reversals of the furnace the air valves to the stack As and A respectively, are the last to be opened. These valves are actually opened only after gas valves to stack Gs and Gs have been opened in each instance a suicient time to allow the heated gas in flue 10 or Hue 13, as the case may be, to pass to the stack, in order that an explosion may not occur due to the mixing of hot gas and air, as previously described.

The mechanism for effecting automatically this sequence of operations will now be described. Referring to Figures 5 and 6, it will be seen that the valve As has its stem ies connected by means-of a cable ZG to a wheel or drum 27 which is fixed on a rotatable shaft 28. Shaft'28 extends through a gear housing 29 and has upon its opposite end a second drum or Wheel 30 to which the end of a cable 31 which supports a counter weight 32, is secured. The counter weight is of a size to substantially balance the weight of the valve AS, A worm wheel in housing 29 meshes with a worm on shaft 33 which is connected to a motor shaft 34 to be driven by motor MS. The housing 29 and motor MS are mounted upon a base casting which is supported above the valve upon any suitable framework, such as that illustrated in Figures 5 and 6. It will be understood thateach of the valves is provided with a similar motor, these motors being diagrammatically illustrated in Figure 12 at MF, MS, NS, N1", N'S, NF, Ms and MF, respectively.

In operation, the circuit through motor MS, for instance, is closed, by mechanism to be hereinafter described, for a suicient length ot time to effect the raising ot valve AS to the desired height, and the circuit is then broken, the worm gear connection between the valve and motor locking the valve against accidental movement when the inotor is stopped. At the instant when the circuit through the motor is broken, or shortly thereafter. the counterweight 32 comes to rest upon the stationary support 36, so that the Weight of the valve is unbalanced and the motor immediately comes to a full stop. To close the Valve the motor is reversed and its rotation continued until the valve is seated, at which time the motor circuit is opened and the motor again stopped.

Referring to Figure 7, a series of spring contacts is indicated at 40, each pair of contacts being connected by su-itable wires to one or more of the valve operating motors. The right hand pair of contacts (i electrically connected to motors MF, NF and MS, as indicated by the printed letters, the second pair of contacts b` to the motors Ms, NYS NF and MF, etc. Extending transversely of spring contacts 40 is a cylinder or drum 41 of insulating material. The ends of spring contacts 40 rest against the surface of this drum, which is mounted to rotate about a fixed axis, and set in the sui-tace of the drum are a plurality of contact plates 42. arranged in pairs, a', b', c, d', e and f, corresponding to the pairs of spring contacts 40.

One plate 42 of each pair is connected by a wire 43 with a contact ring 44 and the other plate of each pair to a contact ring 45 by a second Wire. Contact rings 44 and 45 are electrically connected by spring contacts 46 and 47, respectively, and wires 48 and 49, to the negative and positive terminals'of an electric generator, which may be at any convenient location. Contacts 46 and 4T hear at all times on rings 44 and 45 and it will. therefore, be seen that in a single rotation of drum 41, each ot circuits a, 7), c, nl, c and f will be energized for a length of time depending upon the circumi'erential lengths of the plates, and t-he speed o't' rotation of the drum, inasmuch as each pair of contacts a, c', etc. vill malte contact with the corresponding` spring lingers 40 ot' circuits e, Z), c, etc.

The arrangement of motor circuit-s is such that each motor will be operated twice tor a single revolution ot drinn 41 but the rotations ot the armatures will be in opposite directions in successive operations. For instance, motor NS will be energized when circuit c is closed and will again beenergized when circuit f is closed, but the wires in the two circuits will be reversely connected to the motor armature so that the motor is operated in opposite directions. In this manner the valve AS is opened and closed and in like manner each of the other valves is operated.

As can be seen ltrom Figure 10, the contact plates a. 7)', c', etc.. are arranged symmetricall)v in groups ot three on opposite sides ot drinn 41 but each pair of contacts is spaced longitudinally troni the adjacent pair.

vAlso supported on drum 41 are two contact plates 50 and 50', diametrically opposed, and each extending slightly more than one-half of the way around its circumference. Four contact lingers 51, 52, 53 and 54 are arranged in pairs, the iirst two nientioued being` adapted to bear against plate 50 and the last two against plate 50. Contact lingers 51 and 5S are connected by suitable wircs through the motor R to the negativc terminal ot a generator, and contact lingers 52 and 54 arc connected to stationary switch contacts and 5G, respectively, either one of which may be connected by a switch S to the. positive terminal of the generator. The switch S comprises the main control switch or master switch of the mechanisni, inasmuch as it controls the movement of the motor R and hence, the drinn 41, which is connected to the mot-or through the reducing gearing G, so that by manipulating the switch` the motor R may be energized to rotate the drum and open and close the circuits a, t). e, (l. etc. through the various valve operating motors.

Then the drum is in the position illustrated in Figure 7 and the switch S is in its 'full line position, as shown in this ligure, the contact blades 53 and 54 are insulated from each other. as shown in Figure S, whereas the contact blades 51 and 52 are electrically connected through plate 50. The motor R is, therefore, inactive in this position of the switch but when the switch is moved to its dotted line position, it is energized and causes the rotation of drum 41 lili) at a slow rate of speed. In one particular installation, it was found convenient to design gearing G so that drum 41 rotated through one half of a revolution in thirty four seconds.

In the operation of the device, however, a movement of switch S to its dotted line position will result only in a movement of drum 41 through 180 degrees, inasmuch as spring fingers 51 and 52 can only contact with plate 5() through one-half of a revolution, after which they pass on to the insulating material and become electrically insulated from each other. This breaks the circuit through motor R and stops the drums rotation. Returning the switch to the full line osition will effect a further rotation of 180 egrees, inasmuch as the spring lingers 53 and 54 make contact with plate 50 just before fingers 51 and 52 break contact with plate 50.

The drum 41 comes to rest after each half revolution with all of the circuits a, i, c, d, e and f open so that the 'ialve operating motors are inactive. In Figure 10 is shown the positions of the pairs ot contacts a', b', c', ctc., at the completion ot such a half revolution in the direction of the arrow. The last circuit to be completed was circuit f controlling the motor Ns which operates the air valve to stack As. Movement of switch S to its dotted line position. resulting in movement of drum 41 through 180 degrees, results in the closing first of circuit e, then of circuit cl, and, after a considerable interval, of circuit c, .after which the drum 41 comes to rest. The circumferential lengths of plates 42 determine the intervals during which the motors electrically connected thereto are energized, that is, when considered with the speed of rotation of the drum, aud their relative positions on the surface of the drum determine the sequence in which thc circuits are closed.

It can be seen from Figure 1() that if the speed of rotation of the drum is uniform, that circuits e, d and c are closed the same length of time, which may be five seconds, but that there is a relatively long time interval between the opening of circuit d and the closing of circuit c. Closing of circuit e results in the energization of four valve motors and causes all the valves to be closed, as shown in Diagram 2 of Figure 12. Closing of circuit results in the opening of valves GF, AF and GS, as shown in Diagram 3 and closing of circuit c at a considerable interval thereafter. which may be fifteen seconds, as indicated in Dia am 4 of Fi re 12, results in the opening o valve AS. he drum then comes to rest with all circuits open and awaiting the reversal of switch S. From the foregoing description it will be seen that in a reversal of the furnace the gas valve t0 the stack GS is open for a considerable interval, fifteen seconds in this instance, before the adjacent air valve to the stack is open. This prevents intermixture of hot gas and air and obviates the danger of exploslons.

Instead of connecting spring contacts 51 and 53 directly to the motor R, they are preferably connected by means of a wire 56 to one terminal of the generator, a magnet coil 57 being, however, .included in the circuit. This magnet coil is adapted to attract an armature 58 which comprises n Switch controllinfr the circuit 59 through the armature 60 of the motor. Aniature 58 is nor-I maily in the position shown in Figure llso that circuit-59 is open, a sprin 61 serving to maintain the armature in t is position. Whenever switch S is reversed, however, magnet 57 is energized, armature 58 is moved to the left to close circuit 59, and the motor R becomes active. At the completion of the revolution of drum 41 through 180 degrees, electromagnet 57 becomes de-energized, circuit 59 is opened and circuit 62 closed. This circuit 62 includes a resistance (33, the effect of which is to oppose a braking force to the rotation of armature 60 to eil'ect the practically instantaneous stopping of the motor. f

In the form of the invention above described the opening and closing of the valves is effected by motors, the directions of rota# tion of which isreversed at each operation. It will be seen from the diagrams of Fi re 12 that the wiring is such, as indicate by the and signs, that the olarities of the motors armatures is reverse in opening and closing the valves.

It may be desired to employ motors designed to operate only in one direction, and in Figures 13 to 22`inclusive, valve operating mechanism is described which is adapted to operate in this manner.

In Figure 13 the valve is shown suspended from a crank arm fixed on a rotatable shaft 71 which is supported in housing 72 and which has fixed on its opposite end a crank arm 73 to which the counterweight is hung. Shaft 71 is adapted to be driven through suitable worm eari from motor 74, which isnot reversible. t each energization of this motor by the closing of its circuit, shaft 71 is rotated through 180 degrees, when the motor is deenergized, and the shaft brought to an immediate stop by electro-mechanical mechanism now to be described. The valve is, therefore, seated exactly each time when brought to closed position, .as the motor is prevented from overrunnmg. Y

Also mounted on shaft 71 and at ri ht angles to crank 70 and 73 is a bar 75. xtending into the path of travel of the ends of this bar (Figure 15) is a plunger 76, and a spring 77 normally holdsl itin this position, to obstruct the passage of. bar 75. Plunger 7 6 has a laterally extending portion 77 at its rear end and which is normally engaged by a hook 78 pivotally secured to the forward end of the armature 79 of a solenoid 8() included in the circuit of motor 74. Hook 78 is connected by a link 81 to a two armed trip lever 82, the forward end of which also lies in the path ot' rotating bar 75. Assuming the motor to be at rest and the parts to be in the position in which they are illustrated in Figure 15, it will be seen that upon energization of the motor solenoid 80 immediately becomes active and reti-acts armature 79 which di'aws with it hook 78 and plunger 76 against the action of spring 77 and armature spring 8S. The rearward movement of plunger 76 frees bar which begins to rotate about shaft 71 in the direction of the arrow (Figure 15).

After bar 7 5 has rotated through a short distance, however, it contacts with the forward endrof trip lever 82 and depiesses the saine, thereby raising hook`7 8 and releasing plunger 76 which immediately flics forward due to the action of spring 77. Then shaft 71 has rotated through 180 degrees, thcI opposite end of lever 7 5 strikes plunger 7 and further movement is arrested. At, or immediately before this instant, however, the motor circuit has been broken and solenoid de-energized so that the spring 83 thrusts forward the armature 79 andhook 78, which again engages the rear end of the plunger and the mechanism is again set for sub sequent operation of the motor. It is impossible, therefore, for shaft 71 `to turn through too great an angle, so that thc valve will `become iinseated.

A second form of mechanism for stopping thc rotation of shaft 71 at the proper point consists in an electrically operated brake. ln Figure 18 a brake wheel is illustrated at 82', and in Figure 14 a brake baud 83 is shown, theendsof which are secured to lever 84. This lever is pivoted at 85 and has at its outer end a weight 86. Normally the brake band 83 iS held tightly against the brake wheel 82 by weight 86and this grip of the brake band on the wheel is only interrupted When the brake magnet 87 is energized and lever 84 raised, the magnet being sufficiently strong to overcome the weight 86. A limit switch 88 (Figure 13) is connected by gearing toshaft 71 and becomes operative justas this shaft completes cach 180 degrees of rotation. In Figure 20 the armature of motor 74 is indicated diagraminatically at 74', and the brake magnet'87 and limit switch 88` are also indicated. It will be `seenthat the brakemagnet is in seiies with the limit switch and with the Ymotor, the result being that when the motor rotation of the motor armature. As shaft 71 completes its rotation through 180 degrees, switch 88 is operated, the motor circuit broken, the brakeinagnet cle-energized and the armature promptly stopped, so that the valve will be exactly seated.

In Figures 1G, 17, 18 and 19 the main control switch S for this forni of the invention, and the secondary circuit making andh breaking device are illustrated. The wiring of the control switch S is exactly as in Figure 7, the motor R and the gearing Ur arc also similar, but. the `drum 41', the contact plates thereon, and the spring contacts with which they cooperate are somewhat differcnt. In thisinstance, inasmuch as the valve motors are to be driven in one direction only, only one Contact ring 44 is used, and instead of pairs of contact plates 42 and pairs of spring fingers 40 for conipletiiig the various circuits, each of these circuits is completedby the` Contact of a single spring contact with aV single contact plate. The relative arrangement of the con tact plates and of plates 502 and 503 is, however, the saine as before, so that the motors are operated in the saine sequence and for the same duration of time. In Figure 22 Ashown a` series of diagrams corresponding to the diagrams of Figure 12 previously cxplained, showing` the electrical circuits through the several motors in the. various steps of the reversal of the valves, there being in this instance no reversal of polarity of the motors.

In Figure 21 is illustrated diagrammatically means for retardiiig thespeed of the motor R to prolong the interval in which the gas valve to the stack is open and the air valve to the stack is closed, if this is found to be desirable. A resistance 89 in theiield of the motor is controlled by rheostat arm 90. A spring 91.nornially tends to maintain this arm in such position that the full resistance is in the field circuit. A cam 92, rotatable with drum 41, is adapted to effect movement of the rheostat arm toward the right just after the gas valve to stack has been opened, thereby temporarily cutting` out the resistance 89 and reducing the armature speed and .hence the dr'um speed. Other devices of this character might be used to retard .the speed of the drum, if desired.

From the foregoing description, it will be apparent that numerous other substitutions and modifications of details might be made without departing from the scope of the invention which lis not limited to the several forms disclosed.

The furnace opeiator has, when the fur-- nace is to be reversed, only to reverse the position of the master switch, calling into operation the circuit making and breaking device. The remainder of the operations is lll) entirely automatic and the valve opening and closing is effected in such manner that all danger of ex losion is avoided.

Having thus escribed the invention what is claimed as new and desired to be secured by Letters Patent is:

1. The combination with a furnace having air and gas regenerators, of valves for controlling passages for conducting products of combustion from the furnace to the regenerators, se arate motors for operating the valves, an means for rendering the motors effective to open the valve in the passage leading to the gas regenerator before the valve is opened 1n the passage leading to the associated air regenerator.

2. Mechanism of the class described including in combination a valve, a rotatable member to which said valve is connected, a motor for rotating said rotatable member and means for stoppin the rotation of said rotatable member affer it has rotated throu h 180.

3. echanism of the class described including in combination, a valve, a rotatable member for operating said valve, a motor for rotating said member, and electromechanical means for stopping said motor when said member has rotated through 180.

4. Mechanism of the class described, including in combination, a valve, a rotatable member to which said valve is connected, a motor for rotating said member, a motor circuit, a switch in said motor circuit, means for closing said switch ando ening the same when said rotatable mem r is rotated through substantially 180, and electromechanical means for sto ping the rotation of the motor armature wlien said switch is opened.

5. Mechanism of the class described, including in combination, a valve, a rotatable member to which said valve is connected, a motor for rotating said member, a motor circuit, a switch in said motor circuit, means for closing said switch and opening the same when said rotatable member is rotated through substantially 180, and an electrically operated brake for stopping the rotation of said motor armature when said switch is opened.

6. Mechanism of the class described including in combination, a valve, a rotatable mem-ber connected to said valve for operating the same, a motor for rotating said member, a motor circuit, means for closing said motor circuit and automatically openin the same when said motor has turned sald rotatable member through 180, and electro-mechanical means brought into action by the opening of said circuit for stopping the rotation of the motor armature.

'i'.V In a furnace, the combination of' air and gas regenerators connected to first and second ends-of the furnace, inlet and outlet valves for the regenerators, motors con-I nected respectively to the valves for open? ing and c osing the latter, circuits for the motors, means for closing circuits of the motors for the inlet valves of the regenera- 0 tors at a first end of the furnace and for closing circuits of motors connected to the outlet valves of the regenerators at a second end of the furnace to energize said motors to close the valves, means thereafter effective to close circuits of motors connected to the outlet valves of r enerators at the first end of the furnace an to close the circuit of the motor connected to the outlet valve of the gas regenerator at the second end of the furnace to open said valves, means operative after a predetermined interval to close the circuit of the motor connected to the outlet valve of the air regenerator at the second end of the furnace to Q55 open the latter valve, means for operating said circuit closing means, and motion-limit: ing means associated with the laat-namedN means to render the latter ineffective aftegl-; the inlet valves at the first-named end of 'U3 the furnace and the outlet valves at the second end of the furnace are opened.

8. In a furnace, the combination of air and gas regenerators connected to each end of the furnace, air and gas inlet valves for 93 the air and gas regenerators respectively, outlet valves for the regenerators, electric motors operative to o en and to close the valves, circuits for t e motors including-.. each a pair of contacts, a commutator, con-I 1 00 tacts on the commutator for closing the circuits of motors associated with the air and gas inlet valves for the regenerators at one end of the furnace and with the outlet valves of the regenerators at the other end i of the furnace to render said motors operative for closin said valves, contacts on the commutator isposed rearwardly of' the first contacts considering the direction of n. motion of the commutator for closing circuits of motors for air and gas inlet valves for regenerators at one end of the furnace and for closing a circuit of the motorfor` the outlet valve of the gas regenerator itt'. the other end of the furnace to energize the'` h5 motors to open the valves,.contact means. having its forward end spaced rearwardly f; of the forward end of the second contacts for closing the circuit ofthe motor for the.;V

for each end of the furnace, inlet 4and out- 130 i tl let valves for the regenerators, electric motors for opening and closing the valves, and switch mechanism to control the operation of said motors and including means whereby an air regenerator outlet valve is opened after the associated gas regenerator outlet valve is opened.

10. In a reversible regenerative furnace, the combination of air and gas regenerators for each end of the furnace, inlet and outlet valves for the regenerators, electric motors for opening and closing the valves, switch mechanism to control the operation of said motors and includingr means whereby an air regenerator outlet valve is opened after an associated gas regenerator outlet valve is opened, a motor for operating the switch mechanism, and means for stopping the motor after the switch mechanism has been operated t0 open air inlet valves at one end of the furnace, to close outlet valves at that end, to open the regenerator outlet valves at the other end and to close the regenerator inlet valves at the latter end.

11. In a regenerative furnace, the coinbination of air and gas regenerators for each end of the furnace, inlet and outlet valves for the regenerators, means for producing cyclic operation of the valves wherein an air regenerator outlet valve is opened later than its associated gas regenerator outlet falve, said means including a motor for each valve, circuits for the motors includingr pairs of contacts, a commutator having contacts for making and breaking the circuits, a motor for driving the commutator, limit switch mechanism for breaking the circuit of the last-named motor after a cycle of operation of said valves is completed, and means to apply a braking effect to said motor upon the breaking of its circuit and the completion of a cycle of operation of said valves.

l2. In a regenerative furnace, the combination of air and gas regenerators for each end of the furnace, inlet and outlet valves for the regenerators, means to secure reversible cycle operation of the valves wherein an air regenerator outlet valve is opened after an associated gas regenerator outlet valve is opened, said means including a reversible motor for each valve, circuits for the motors, switch mechanism for making and breaking the circuits and including a movable element, a motor for driving the movable element of the switch mechanism, overlapping contacts carried by said movable element, a pair of contacts adapted to engage each of the overlapping contacts, a master switch for completing a circuit for the last-named motor through a pair of contacts in engagement with an overlapping contact to operate said motor to move the movable switch element, and braking means rendered efective by ,the disengagement of an overlapping contact from a pair of active contacts to stop the motor with the other pair of contacts in engagement with the other overlapping contact upon the completion of a cycle of valve operation.

13. In a regenerative furnace, the combination of air and gas regenerators for each end of the furnace, inlet and outlet valves for the regenerators, means to secure reversible cyclic operation of the valves wherein an air regenerator outlet valve is opened after an associated gas regenerator outlet valve is opened, said means including a reversible motor for each valve, circuits for the motors, switch mechanism for making and bruiking the circuits of said motors to secure c vclic operation of the valves, said switch mechanism including a rotary drum having contacts thereon for making and breaking the motor circuits, a motor for driving the drum, overlapping segmental contacts carried by the drum, a pair of contacts adapted to engage with each of said overlapping segmental contacts, a switch for completing a circuit through a pair of contacts in engagement with a segmental contact and said motor to operate the latter to rotate the. drum, and electro-dynamic braking means rendered effective by a segmental' contact passing out of engagement with a pair of cont-acts in order to stop the motor with the other pair of contacts in engagemeut with the other segmental contact upon completion of a cycle of valve operation. In testimony whereof I hereunto affix my signature.

CHARLES PRENTICE TURNER. 

